The present invention relates to retrievable downhole tools used in hydraulically actuating components in a well. More particularly, this invention achieves significantly increased control of the downhole tool by isolating the inlet port to the hydraulic actuating mechanism of the tool. The downhole tool may be a retrievable running tool used in a liner hanger setting operation, and may include a port isolation for controlling fluid pressure to set a slip of a liner hanger, or to release the running tool from the set liner hanger in order to retrieve the running tool to the surface.
Various downhole tools include hydraulic actuating mechanism which are responsive to fluid pressure to move downhole component from an unset position to a set position. For example, a liner hanger running tool is conventionally operated by dropping a ball through the liner hanger to seal on a seat of a landing collar at the lower end of the liner. A ball lands on the seat to increase fluid pressure within the liner hanger setting assembly to set the slips on the running tool. Subsequently, fluid pressure in the running tool may also be used to release the running tool from the set liner hanger.
A significant problem with hydraulically actuated downhole tools is that such tools may prematurely move the actuating mechanism and thus prematurely xe2x80x9csetxe2x80x9d the tool due to an unexpected increase in fluid pressure in the running string and thus within the tool. Hydraulically activated downhole tools may thus be prematurely set either when running the tool to its desired location within the well, or when the tool is positioned at its desired location but before the particular actuating mechanism was intended to be set. Various attempts to reduce this premature setting problem have not been commercially successful.
In an attempt to avoid the above described problems, some downhole tools have used pick up and latching techniques in a setting tool to form a pressure chamber that then allows the packer to be set, as disclosed in U.S. Pat. Nos. 6,009,943 and 5,884,702. Other systems have been attempted to use a complex rotary ball valve mechanism which rotates about the ball seat, as disclosed in U.S. Pat. No. 5,553,672. U.S. Pat. No. 5,968,881 discloses a ball seat which is shifted to close off a port in a surge protection tool after a ball lands on the seat. Port isolation techniques have also been used in downhole washing tools for washing down a liner.
Various downhole tools utilize a segmented ball seat with collet fingers which are shifted from a contracted position to an expanded position to allow a ball to drop through the segmented ball seat, as shown in U.S. Pat. Nos. 4,825,037, 4,926,939 and 5,244,044. These segmented ball seat designs include collet fingers which may fail to seal properly with the ball, thereby preventing the required pressure build up so that the collet fingers may expand and let the ball drop through the seat. Moreover, wellbore fluids that pass between the collet fingers cause erosion and may result in failure of the ball seat.
Many downhole running tools which are used to conduct wellbore operations must have a sizeable throughbore in the central body of the tool, either for passing a required amount of fluid with a relatively low pressure drop, or for allowing another tool, such as a ball, a plug, or a wireline tool, to freely pass through the bore of the running tool while in the well. In liner hanger setting operations, this through bore in the liner hanger setting tool may be sized to pass balls or plugs which are used to set the liner hanger and to conduct cementing operations. Consequently, many liner hanger setting operations land the ball in the landing collar at the lower end of the liner, as described above, to increase fluid pressure to the setting port. Other liner hanger setting tools avoid the benefits of a hydraulically actuated tool and instead use mechanical pick up and latching techniques to set the liner hanger within the well.
The disadvantages of the prior art are overcome by the present invention, and an improved running tool and method of hydraulically actuating a downhole tool are hereinafter disclosed.
In one embodiment, the retrievable hydraulically operated running tool includes a tubular body for suspending in the wellbore from a conveyance tubular, a piston in fluid communication with a fluid inlet port in the tubular body and moveable from an initial position to an activated position in response to fluid pressure, a port isolation sleeve axially moveable with respect to the tubular body from a port isolation position to an open port position, a seat supported on the sleeve such that fluid pressure increases when a ball lands to shift the sleeve, and a release mechanism for releasing the ball from the seat. The hydraulically operated running tool may be used, for example, as a liner hanger running tool to perform a selected operation as part of the overall liner hanger setting operation. The ball may land on the seat to substantially seal off the bore in the tubular body. The seat may thereafter be permanently deformed in response to increased fluid pressure to pass the ball through the seat, or the seat may otherwise yield or release the ball from the seat.
It is an object of the present invention to provide a method of operating a retrievable running tool of the type discussed above. The port isolation technique of the present invention provides a substantially reliable method of performing a downhole tool activation with a significantly decreased risk that the downhole tool will be prematurely activated.
It is an object of the present invention to provide a hydraulically actuated running tool which reliably prevents premature actuation by controllably isolating the inlet port to the hydraulic actuating mechanism of the tool.
A related object of the invention is to provide a downhole tool with a port isolation system which maintains a large throughbore through the running tool.
It is a significant feature of the invention that the hydraulically activated downhole tool will not prematurely activate in response to either an over-pressure condition within the bore of the tool.
It is a feature of the present invention that the running tool of the present invention may be used in a liner hanger setting operation. A ball may be landed on a seat within a sleeve which isolates the inlet port to set the slips and thus hang off the liner within the casing. Another sleeve may provide port isolation for hydraulically releasing the running tool from the set liner hanger. In each case, the ball lands on the seat and shifts the sleeve to open the inlet port, so that fluid pressure within the running tool may then be used to achieve the desired downhole actuation. Accordingly, the actuating mechanism is prevented by the sleeve from prematurely setting the running tool. The ball is landed on a seat and shifts the sleeve so that pressure can thereafter hydraulically actuate the running tool with the open inlet port. The ball may thereafter be pumped through the seat, which may be permanently deformed to enlarge the through bore in the running tool or otherwise yield to release the ball from the seat. The ball may then be pumped to a lower seat on another shiftable sleeve, or may be pumped to a ball catch either within the running tool or at the lower end of the tubular string.
A significant advantage of the present invention is that the complexity of the running tool is not significantly increased, conventional well operating procedures are utilized, and the reliability of the downhole tool performing its desired operation when intended is significantly increased utilizing components which individually are well known in the art. Operators of wells have long desired improved running tools and methods which increase tool reliability and thus reduce the risk of either a prematurely set liner hanger or a prematurely released running tool.